With the rapid development of display technology, capacitive touch display devices have been widespread in people's lives. Currently, a capacitive touch display device detects a touch position by utilization of the mutual-capacitance or self-capacitive principle. Compared with the touch display device employing the mutual-capacitance principle, the touch display device employing the self-capacitive principle can effectively improve the signal-to-noise ratio (SNR) of touch and improve the accuracy of touch sensing, and hence receives wide attention.
Generally, the touch display device employing the self-capacitive principle comprises a plurality of self-capacitive electrodes which are arranged in the same layer and insulated from each other. When the screen is not touched by a touch object, the capacitance of the self-capacitive electrode is at a fixed value, and the time of charging the capacitor is also at a fixed value. When the screen is touched by the touch object, the capacitance of corresponding self-capacitive electrode changes and the time of charging the capacitor changes as well, so that a touch chip can determine the touch position by detecting the variation of the charging time of the self-capacitive electrode in the touch period.